/* -*- P4_16 -*- */
#include <core.p4>
#include <v1model.p4>

// 常量定义部分
const bit<16> PROTOCOL_IPV4 = 0x800;
const bit<16> PROTOCOL_ARP = 0x0806;

const bit<16> ARP_HW_ETHERNET = 0x0001;
const bit<16> ARP_PROTO_IPV4 = 0x0800;
const bit<8> ARP_HW_LEN_ETHERNET = 6;
const bit<8> ARP_PROTO_LEN_IPV4 = 4;
const bit<16> ARP_REQUEST = 1;
const bit<16> ARP_REPLY = 2;

// 类型定义部分
typedef bit<9> PortNumber;
typedef bit<48> MacAddr;
typedef bit<32> IPv4Addr;

// 头部定义部分
header EthernetHdr {
    MacAddr dstMac;
    MacAddr srcMac;
    bit<16> protocolType;
}

header IPv4Hdr {
    bit<4> version;
    bit<4> headerLen;
    bit<8> diffService;
    bit<16> totalLength;
    bit<16> packetId;
    bit<3> fragFlags;
    bit<13> fragOffset;
    bit<8> ttl;
    bit<8> upperProtocol;
    bit<16> checksum;
    IPv4Addr srcIp;
    IPv4Addr dstIp;
}

header ArpHdr {
    bit<16> hardwareType;
    bit<16> protocol;
    bit<8> hardwareAddrLen;
    bit<8> protocolAddrLen;
    bit<16> opCode;
    MacAddr senderMac;
    IPv4Addr senderIp;
    MacAddr targetMac;
    IPv4Addr targetIp;
}

// 元数据定义部分
struct PacketMetadata {
    IPv4Addr arpTarget;
}

// 组合头部结构体
struct AllHeaders {
    EthernetHdr eth;
    IPv4Hdr ipv4;
    ArpHdr arp;
}

// 解析器部分
parser PacketParse(
    packet_in packet,
    out AllHeaders headers,
    inout PacketMetadata meta,
    inout standard_metadata_t stdMeta
) {
    state start {
        transition parseEth;
    }

    state parseEth {
        packet.extract(headers.eth);
        switch (headers.eth.protocolType) {
            case PROTOCOL_IPV4:
                transition parseIPv4;
            case PROTOCOL_ARP:
                transition parseARP;
            default:
                transition accept;
        }
    }

    state parseIPv4 {
        packet.extract(headers.ipv4);
        transition accept;
    }

    state parseARP {
        packet.extract(headers.arp);
        meta.arpTarget = headers.arp.targetIp;
        transition accept;
    }
}

// 校验和验证部分
control ChecksumCheck {
    apply {
        // 可添加校验和验证逻辑
    }
}

// 入口控制逻辑部分
control IngressLogic {
    action DiscardPacket() {
        mark_to_drop(standard_metadata);
    }

    action RouteIPv4(PortNumber outPort, MacAddr dstMac) {
        standard_metadata.egress_spec = outPort;
        headers.eth.srcMac = MySwitchMAC; // 假设 MySwitchMAC 为交换机 MAC 常量
        headers.eth.dstMac = dstMac;
        headers.ipv4.ttl = headers.ipv4.ttl - 1;
        if (headers.arp.isValid()) {
            headers.arp.setInvalid();
        }
    }

    action RespondARP(MacAddr switchMac, IPv4Addr switchIp) {
        headers.eth.dstMac = headers.arp.senderMac;
        headers.eth.srcMac = switchMac;
        headers.arp.opCode = ARP_REPLY;
        headers.arp.senderMac = switchMac;
        headers.arp.senderIp = switchIp;
        headers.arp.targetMac = headers.arp.senderMac;
        headers.arp.targetIp = headers.arp.senderIp;
        standard_metadata.egress_spec = standard_metadata.ingress_port;
        if (headers.ipv4.isValid()) {
            headers.ipv4.setInvalid();
        }
    }

    table IPv4RouteTable {
        key = {
            headers.ipv4.dstIp: lpm;
        }
        actions = {
            RouteIPv4;
            DiscardPacket;
            NoAction;
        }
        size = 2048;
        default_action = NoAction();
    }

    table ARPProcessTable {
        key = {
            headers.arp.opCode: exact;
            headers.arp.targetIp: lpm;
        }
        actions = {
            RespondARP;
            DiscardPacket;
        }
        size = 1024;
        default_action = DiscardPacket();
    }

    apply {
        if (headers.eth.protocolType == PROTOCOL_IPV4) {
            IPv4RouteTable.apply();
        } else if (headers.eth.protocolType == PROTOCOL_ARP) {
            ARPProcessTable.apply();
        }
    }
}

// 出口控制逻辑部分
control EgressLogic {
    apply {
        // 可扩展功能
    }
}

// 校验和计算部分
control ChecksumCompute {
    apply {
        if (headers.ipv4.isValid()) {
            update_checksum(
                true,
                { headers.ipv4.version, headers.ipv4.headerLen, headers.ipv4.diffService,
                  headers.ipv4.totalLength, headers.ipv4.packetId, headers.ipv4.fragFlags,
                  headers.ipv4.fragOffset, headers.ipv4.ttl, headers.ipv4.upperProtocol,
                  headers.ipv4.srcIp, headers.ipv4.dstIp },
                headers.ipv4.checksum,
                HashAlgorithm.csum16
            );
        }
    }
}

// 反解析器部分
control PacketReassemble {
    apply {
        packet.emit(headers.eth);
        if (headers.ipv4.isValid()) {
            packet.emit(headers.ipv4);
        }
        if (headers.arp.isValid()) {
            packet.emit(headers.arp);
        }
    }
}

// 主程序定义部分
V1Switch(
    PacketParse(),
    ChecksumCheck(),
    IngressLogic(),
    EgressLogic(),
    ChecksumCompute(),
    PacketReassemble()
) main;    